U.S. patent application number 12/207123 was filed with the patent office on 2009-03-19 for radar apparatus, method for controlling the same, and vehicle including the same.
This patent application is currently assigned to MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD.. Invention is credited to Kenichi INOUE, Daisuke UEDA.
Application Number | 20090073025 12/207123 |
Document ID | / |
Family ID | 40453892 |
Filed Date | 2009-03-19 |
United States Patent
Application |
20090073025 |
Kind Code |
A1 |
INOUE; Kenichi ; et
al. |
March 19, 2009 |
RADAR APPARATUS, METHOD FOR CONTROLLING THE SAME, AND VEHICLE
INCLUDING THE SAME
Abstract
Provided is a radar apparatus that detects an object, and
includes: an oscillating unit for generating carrier waves; first
and second transmission units for spreading the carrier waves,
respectively using a first pseudo-random code and a second
pseudo-random code different from the first pseudo-random code; a
first transmission antenna for transmitting the carrier waves
spread by the first transmission unit; a second transmission
antenna for transmitting the carrier waves spread by the second
transmission unit and have a directional characteristic different
from that of the carrier waves transmitted by the first
transmission antenna; a reception antenna for receiving reflected
waves that are the carrier waves that have been transmitted by the
first and second transmission antennas and have been reflected from
the object; and a reception unit for despreading the reflected
waves, using the first pseudo-random code and despreading the
reflected waves, using the second pseudo-random code.
Inventors: |
INOUE; Kenichi; (Osaka,
JP) ; UEDA; Daisuke; (Osaka, JP) |
Correspondence
Address: |
GREENBLUM & BERNSTEIN, P.L.C.
1950 ROLAND CLARKE PLACE
RESTON
VA
20191
US
|
Assignee: |
MATSUSHITA ELECTRIC INDUSTRIAL CO.,
LTD.
Osaka
JP
|
Family ID: |
40453892 |
Appl. No.: |
12/207123 |
Filed: |
September 9, 2008 |
Current U.S.
Class: |
342/70 ;
342/175 |
Current CPC
Class: |
G01S 2013/93274
20200101; G01S 2013/93272 20200101; G01S 13/325 20130101; G01S
13/931 20130101; G01S 2013/93271 20200101 |
Class at
Publication: |
342/70 ;
342/175 |
International
Class: |
G01S 13/93 20060101
G01S013/93; G01S 13/00 20060101 G01S013/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 13, 2007 |
JP |
2007-238358 |
Claims
1. A radar apparatus that detects an object, said radar apparatus,
comprising: an oscillating unit configured to generate carrier
waves; a first transmission unit configured to spread the carrier
waves generated by said oscillating unit, using a first
pseudo-random code; a second transmission unit configured to spread
the carrier waves generated by said oscillating unit, using a
second pseudo-random code different from the first pseudo-random
code; a first transmission antenna that transmits first carrier
waves that are the carrier waves spread by said first transmission
unit; a second transmission antenna that transmits second carrier
waves that are the carrier waves spread by said second transmission
unit, the second carrier waves having a directional characteristic
being different from a directional characteristic of the first
carrier waves transmitted by said first transmission antenna; a
reception antenna that receives reflected waves that are the first
carrier waves and the second carrier waves that have been
transmitted respectively by said first transmission antenna and
said second transmission antenna and have been reflected from the
object; and a reception unit configured to despread the reflected
waves received by said reception antenna, using the first
pseudo-random code and to despread the reflected waves received by
said reception antenna, using the second pseudo-random code.
2. The radar apparatus according to claim 1, wherein the first
carrier waves transmitted by said first transmission antenna cover
a range of a longer distance and a narrower angle than a range of
the second carrier waves transmitted by said second transmission
antenna.
3. The radar apparatus according to claim 1, wherein said first
transmission antenna includes third transmission antennas, said
second transmission antenna includes fourth transmission antennas
that are less than said third transmission antennas in number, said
third transmission antennas and said fourth transmission antennas
are respectively disposed linearly in a first direction; and said
third transmission antennas and said fourth transmission antennas
are respectively disposed symmetric with respect to a second
direction perpendicular to the first direction.
4. The radar apparatus according to claim 3, wherein each of said
fourth transmission antennas is disposed to be paired with said
third transmission antennas; and in the first direction, (i) the
pairs of said third transmission antennas and said fourth
transmission antennas are sandwiched between the other of said
third transmission antennas that are not paired with said fourth
transmission antennas, or (ii) said third transmission antennas
that are not paired with said fourth transmission antennas are
sandwiched between the pairs of said fourth transmission antennas
and the other of said third transmission antennas.
5. The radar apparatus according to claim 1, further comprising a
gain adjusting unit configured to adjust a gain of the first
carrier waves transmitted by said first transmission antenna to be
larger than a gain of the second carrier waves transmitted by said
second transmission antenna.
6. The radar apparatus according to claim 1, wherein said reception
unit includes: a first selecting unit configured to select one of
the first pseudo-random code and the second pseudo-random code; a
despreading unit configured to despread, using one of the first
pseudo-random code and the second pseudo-random code selected by
said first selecting unit, the reflected waves received by said
reception antenna; and a detecting unit configured to detect the
reflected waves despread by said despreading unit, using the
carrier waves generated by said oscillating unit.
7. The radar apparatus according to claim 1, wherein said reception
unit includes: a splitting unit configured to split the reflected
waves received by said reception antenna into first reflected waves
and second reflected waves; a first despreading unit configured to
despread the first reflected waves using the first pseudo-random
code; a first detecting unit configured to detect the first
reflected waves despread by said first despreading unit, using the
carrier waves generated by said oscillating unit; a second
despreading unit configured to despread the second reflected waves,
using the second pseudo-random code; and a second detecting unit
configured to detect the second reflected waves despread by said
second despreading unit, using the carrier waves generated by said
oscillating unit.
8. The radar apparatus according to claim 1, wherein said reception
antenna includes a first reception antenna and a second reception
antenna, and said reception unit includes: a first despreading unit
configured to despread reflected waves received by said first
reception antenna, using the first pseudo-random code; a first
detecting unit configured to detect the reflected waves despread by
said first despreading unit, using the carrier waves generated by
said oscillating unit; a second despreading unit configured to
despread reflected waves received by said second reception antenna,
using the second pseudo-random code; and a second detecting unit
configured to detect the reflected waves despread by said second
despreading unit, using the carrier waves generated by said
oscillating unit.
9. The radar apparatus according to claim 1, further comprising: a
code generating unit configured to generate a third pseudo-random
code, a fourth pseudo-random code, and a fifth pseudo-random code;
a first OR circuit that generates the first pseudo-random code by
calculating an exclusive OR of the third and fourth pseudo-random
codes; and a second OR circuit that generates the second
pseudo-random code by calculating an exclusive OR of the third and
fifth pseudo-random codes.
10. The radar apparatus according to claim 9, wherein said
reception unit includes: a first despreading unit; a second
despreading unit; a third despreading unit; and a second selecting
unit configured to assign the third, fourth, and fifth
pseudo-random codes to said first despreading unit, said second
despreading unit, and said third despreading unit, wherein said
first despreading unit is configured to despread the reflected
waves received by said reception antenna, using one of the third,
fourth, and fifth pseudo-random codes assigned by said second
selecting unit, said second despreading unit is configured to
despread the reflected waves received by said reception antenna,
using one of the third, fourth, and fifth pseudo-random codes
assigned by said second selecting unit, said third despreading unit
is configured to despread the reflected waves despread by said
first despreading unit and the reflected waves despread by said
second despreading unit, using one of the third, fourth, and fifth
pseudo-random codes assigned by said second selecting unit, and
said reception unit includes a detecting unit configured to detect
the reflected waves despread by said third despreading unit, using
the carrier waves generated by said oscillating unit.
11. A vehicle, comprising a radar apparatus that detects an object,
wherein said radar apparatus includes: an oscillating unit
configured to generate carrier waves; a first transmission unit
configured to spread the carrier waves generated by said
oscillating unit, using a first pseudo-random code; a second
transmission unit configured to spread the carrier waves generated
by said oscillating unit, using a second pseudo-random code
different from the first pseudo-random code; a first transmission
antenna that transmits first carrier waves that are the carrier
waves spread by said first transmission unit; a second transmission
antenna that transmits second carrier waves that are the carrier
waves spread by said second transmission unit, the second carrier
waves having a directional characteristic being different from a
directional characteristic of the first carrier waves transmitted
by said first transmission antenna; a reception antenna that
receives reflected waves that are the first carrier waves and the
second carrier waves that have been transmitted respectively by
said first transmission antenna and said second transmission
antenna and have been reflected from the object; and a reception
unit configured to despread the reflected waves received by said
reception antenna, using the first pseudo-random code and to
despread the reflected waves received by said reception antenna,
using the second pseudo-random code, said first transmission
antenna transmits the first carrier waves spread by said first
transmission unit, forward of the vehicle, and said second
transmission antenna transmits the second carrier waves spread by
said second transmission unit, at least forward or diagonally
forward of the vehicle.
12. A method for controlling a radar apparatus that detects an
object, said method comprising: generating carrier waves; spreading
the carrier waves using a first pseudo-random code, and spreading
the carrier waves using a second pseudo-random code different from
the first pseudo-random code; transmitting first carrier waves and
second carrier waves, the first carrier waves being the carrier
waves spread using the first pseudo-random code, and the second
carrier waves being the carrier waves spread using the second
pseudo-random code and having a directional characteristic
different from a directional characteristic of the first carrier
waves; receiving reflected waves that are the first carrier waves
and the second carrier waves and that have been transmitted and
have been reflected from the object; and despreading the reflected
waves using the first pseudo-random code, and the reflected waves
using the second pseudo-random code.
Description
BACKGROUND OF THE INVENTION
[0001] (1) Field of the Invention
[0002] The present invention relates to a radar apparatus, a method
for controlling the same, and a vehicle including the same, and
more particularly to a radar apparatus that transmits a
multiplicity of carrier waves having different directional
characteristics, and detects an object.
[0003] (2) Description of the Related Art
[0004] Vehicles have been equipped with on-vehicle radar
apparatuses for preventing collision with other vehicles and
detection of obstacles. The on-vehicle radar apparatuses have
different detection ranges (detection distances and directions)
depending on statuses of the vehicles. For example, while
traveling, the on-vehicle radar apparatuses detect an obstacle
approximately 100 meters forward. Furthermore, when the vehicles
are backing up, the on-vehicle radar apparatuses detect an obstacle
in a wider area approximately 10 meters backward of the
vehicles.
[0005] Furthermore, when the vehicles are traveling, the on-vehicle
radar apparatuses need to detect obstacles at different distances
and in different directions, depending on a traveling direction of
the vehicles. For example, the on-vehicle radar apparatuses need to
detect obstacles at a long distance in a straightforward direction.
In the case of diagonally forward of the vehicles, the on-vehicle
radar apparatuses need to detect not obstacles at a long distance,
but obstacles in a wider area with respect to the vehicles.
[0006] For such requirements, for example, Japanese Unexamined
Patent Application Publication No. 10-27299 (referred to
hereinafter as Patent Reference 1) discloses an on-vehicle radar
apparatus that emits, straight forward of a vehicle, a beam having
a narrower width and that emits, in a diagonally forward direction
closer to a side of the vehicle, a beam having a wider width.
[0007] FIG. 1 illustrates a block diagram of a conventional
on-vehicle radar apparatus described in Patent Reference 1. A radar
apparatus 100 illustrated in FIG. 1 includes a distance and speed
detecting unit 101, a signal processing unit 102, and a switched
mode multi-beam antenna 103.
[0008] The multi-beam antenna 103 includes antennas 104, 105, and
106, and a switch 107.
[0009] The antenna 104 emits a beam 111 diagonally forward left of
a vehicle equipped with the radar apparatus 100. The antenna 105
emits a beam 110 forward of the vehicle. The antenna 106 emits a
beam 112 diagonally forward right of the vehicle.
[0010] The beam 110 detects an obstacle at a long distance, and has
a narrower beam width. The beams 111 and 112 detect an obstacle at
a short distance, and have a wider beam width.
[0011] The switch 107 switches between the antennas 104, 105, and
106 for emitting a beam.
[0012] When the beam emitted from one of the antenna 104, 105, and
106 is reflected from an obstacle, the one of the antenna 104, 105,
and 106 that has emitted the beam receives the reflected beam.
[0013] The signal processing unit 102 performs signal processing,
such as analog-digital conversion, on the beam received by the one
of the antenna 104, 105, and 106. The distance and speed detecting
unit 101 detects, based on a signal obtained through the signal
processing by the signal processing unit 102, a distance from the
vehicle equipped with the radar apparatus 100 to the obstacle, a
relative speed with respect to the obstacle, and other
information.
[0014] With such a configuration, the conventional radar apparatus
100 can switch between detection ranges by switching between the
antennas 104, 105, and 106 using the switch 107.
[0015] Furthermore, for example, Japanese Unexamined Patent
Application Publication No. 8-262133 (referred to hereinafter as
Patent Reference 2) discloses a radar apparatus that switches
between radio waves emitted from an antenna in a time-sharing mode.
The radar apparatus disclosed in Patent Reference 2 is an FM radar
apparatus, and transmits FM signals having a predetermined level,
from antennas at different times. The radar apparatus switches
between the FM signals using a switch.
[0016] However, both of the conventional radar apparatuses
disclosed in Patent References 1 and 2 need to select, using a
certain switch (for example, an electronic switching device), one
of transmission antennas, or the transmission antennas alternately
in a time-sharing mode in order to switch between detection
distances and detection directions of the vehicle equipped with one
of the radar apparatuses. Furthermore, some on-vehicle radar
apparatuses use pulses or carrier waves having millimeter or quasi
millimeter wave frequencies. In other words, switching devices need
to be interposed in transmission paths having a high frequency up
to several tens of GHz. Thus, the conventional radar apparatuses
need to be controlled without any influence of reflection, loss,
and change of waves with the passage of time in such transmission
paths. In other words, there is a problem that designing of the
conventional radar apparatuses has difficulty due to necessity of
switching devices.
[0017] In general, a GaAs PIN diode and others are used as such
switching devices. Costly switching devices further increase the
cost of radar apparatuses. In other words, the conventional radar
apparatuses including such switching devices have a problem of
increased costs.
SUMMARY OF THE INVENTION
[0018] In view of the problems described above, the present
invention has an object of providing a radar apparatus capable of
changing detection distances and detection directions of a vehicle,
a method for controlling the same, and a vehicle including the
same, without providing any switching device in a transmission path
of carrier waves.
[0019] In order to achieve the object, the radar apparatus
according to the present invention detects an object, and includes:
an oscillating unit configured to generate carrier waves; a first
transmission unit configured to spread the carrier waves generated
by the oscillating unit, using a first pseudo-random code; a second
transmission unit configured to spread the carrier waves generated
by the oscillating unit, using a second pseudo-random code
different from the first pseudo-random code; a first transmission
antenna that transmits first carrier waves that are the carrier
waves spread by the first transmission unit; a second transmission
antenna that transmits second carrier waves that are the carrier
waves spread by the second transmission unit, the second carrier
waves having a directional characteristic being different from a
directional characteristic of the first carrier waves transmitted
by the first transmission antenna; a reception antenna that
receives reflected waves that are the first carrier waves and the
second carrier waves that have been transmitted respectively by the
first transmission antenna and the second transmission antenna and
have been reflected from the object; and a reception unit
configured to despread the reflected waves received by the
reception antenna, using the first pseudo-random code and to
despread the reflected waves received by the reception antenna,
using the second pseudo-random code.
[0020] With this configuration, the radar apparatus according to
the present invention transmits carrier waves that have different
directional characteristics and that have been spread using
different pseudo-random codes. Furthermore, the radar apparatus
according to the present invention despreads the first and second
carrier waves that are reflected from an object, using 2
pseudo-random codes, respectively. Thereby, the carrier waves
having different directional characteristics can be extracted
separately and equivalently. Thus, the radar apparatus can switch
between two different detectable areas with detection distances and
directions of a vehicle without interposing a switching device in a
transmission path of carrier wave of several tens of GHz.
[0021] Furthermore, the first carrier waves transmitted by the
first transmission antenna may cover a range of a longer distance
and a narrower angle than a range of the second carrier waves
transmitted by the second transmission antenna.
[0022] With this configuration, the radar apparatus according to
the present invention can detect an object by switching between a
detection range of a longer distance and a narrower angle and a
detection range of a shorter distance and a wider angle.
[0023] Furthermore, the first transmission antenna may include
third transmission antennas, the second transmission antenna may
include fourth transmission antennas that are less than the third
transmission antennas in number, the third transmission antennas
and the fourth transmission antennas may be respectively disposed
linearly in a first direction; and the third transmission antennas
and the fourth transmission antennas may be respectively disposed
symmetric with respect to a second direction perpendicular to the
first direction. With this configuration, the radar apparatus
according to the present invention can detect a range symmetric
with respect to a vehicle, forward and diagonally forward of the
vehicle.
[0024] Furthermore, each of the fourth transmission antennas may be
disposed to be paired with the third transmission antennas; and in
the first direction, (i) the pairs of the third transmission
antennas and the fourth transmission antennas may be sandwiched
between the other of the third transmission antennas that are not
paired with the fourth transmission antennas, or (ii) the third
transmission antennas that are not paired with the fourth
transmission antennas may be sandwiched between the pairs of the
fourth transmission antennas and the other of the third
transmission antennas.
[0025] With this configuration, since the third transmission
antennas are larger in number than the fourth transmission
antennas, the first carrier waves transmitted by the first
transmission antenna can have a range of a longer distance and a
narrower angle. In other words, the radar apparatus according to
the present invention can detect an object by switching between a
detection range of a longer distance and a narrower angle and a
detection range of a shorter distance and a wider angle.
[0026] Furthermore, the third transmission antennas are disposed to
be paired with the fourth transmission antennas, and the pairs of
the third transmission antennas and the fourth transmission
antennas are disposed symmetric linearly inward or outward of the
pairs of third transmission antennas and the fourth transmission
antennas. Thereby, the third transmission antennas and the fourth
transmission antennas can be designed each as a linear array
antenna while maintaining a symmetrical property of a detection
range with respect to right and left directions of the vehicle.
[0027] Furthermore, the radar apparatus may further include a gain
adjusting unit configured to adjust a gain of the first carrier
waves transmitted by the first transmission antenna to be larger
than a gain of the second carrier waves transmitted by the second
transmission antenna.
[0028] With this configuration, the gain adjusting unit can easily
set ranges of the first and second carrier waves transmitted by the
first transmission antenna and the second transmission antenna,
respectively. For example, a range of the first carrier waves
transmitted from the first transmission antenna can be easily
expanded to a longer distance by increasing electric power of the
carrier waves transmitted from the first transmission antenna more
than that of the second carrier waves transmitted from the second
transmission antenna.
[0029] Furthermore, the reception unit may include: a first
selecting unit configured to select one of the first pseudo-random
code and the second pseudo-random code; a despreading unit
configured to despread, using one of the first pseudo-random code
and the second pseudo-random code selected by the first selecting
unit, the reflected waves received by the reception antenna; and a
detecting unit configured to detect the reflected waves despread by
the despreading unit, using the carrier waves generated by the
oscillating unit.
[0030] With this configuration, one despreading unit and one
detecting unit can despread and detect waves using selectively 2
pseudo-random codes, because the first selecting unit selects a
pseudo-random code to be used for despreading. Thus, a circuit area
in a reception unit can be reduced.
[0031] Furthermore, the reception unit may include: a splitting
unit configured to split the reflected waves received by the
reception antenna into first reflected waves and second reflected
waves; a first despreading unit configured to despread the first
reflected waves using the first pseudo-random code; a first
detecting unit configured to detect the first reflected waves
despread by the first despreading unit, using the carrier waves
generated by the oscillating unit; a second despreading unit
configured to despread the second reflected waves, using the second
pseudo-random code; and a second detecting unit configured to
detect the second reflected waves despread by the second
despreading unit, using the carrier waves generated by the
oscillating unit.
[0032] With this configuration, waves can be despread and detected
in parallel using different pseudo-random codes. Thus, the
processing speed of the reception circuit can be improved.
[0033] Furthermore, the reception antenna may include a first
reception antenna and a second reception antenna, and the reception
unit may include: a first despreading unit configured to despread
reflected waves received by the first reception antenna, using the
first pseudo-random code; a first detecting unit configured to
detect the reflected waves despread by the first despreading unit,
using the carrier waves generated by the oscillating unit; a second
despreading unit configured to despread reflected waves received by
the second reception antenna, using the second pseudo-random code;
and a second detecting unit configured to detect the reflected
waves despread by the second despreading unit, using the carrier
waves generated by the oscillating unit.
[0034] With this configuration, waves can be despread and detected
in parallel using different pseudo-random codes. Thus, the
processing speed of the reception circuit can be improved.
[0035] Furthermore, the radar apparatus may further include: a code
generating unit configured to generate a third pseudo-random code,
a fourth pseudo-random code, and a fifth pseudo-random code; a
first OR circuit that generates the first pseudo-random code by
calculating an exclusive OR of the third and fourth pseudo-random
codes; and a second OR circuit that generates the second
pseudo-random code by calculating an exclusive OR of the third and
fifth pseudo-random codes.
[0036] With this configuration, the carrier waves can be spread
using gold-sequence pseudo-random codes. Thus, various
pseudo-random codes can be used easily.
[0037] Furthermore, the reception unit may include: a first
despreading unit; a second despreading unit; a third despreading
unit; and a second selecting unit configured to assign the third,
fourth, and fifth pseudo-random codes to the first despreading
unit, the second despreading unit, and the third despreading unit,
wherein the first despreading unit may be configured to despread
the reflected waves received by the reception antenna, using one of
the third, fourth, and fifth pseudo-random codes assigned by the
second selecting unit, the second despreading unit may be
configured to despread the reflected waves received by the
reception antenna, using one of the third, fourth, and fifth
pseudo-random codes assigned by the second selecting unit, the
third despreading unit may be configured to despread the reflected
waves despread by the first despreading unit and the reflected
waves despread by the second despreading unit, using one of the
third, fourth, and fifth pseudo-random codes assigned by the second
selecting unit, and the reception unit may include a detecting unit
configured to detect the reflected waves despread by the third
despreading unit, using the carrier waves generated by the
oscillating unit.
[0038] With this configuration, one of the carrier waves spread by
any pseudo-random code obtained through an exclusive OR of 2
pseudo-random codes can be selectively extracted.
[0039] Furthermore, the vehicle according to the present invention
includes a radar apparatus that detects an object, wherein the
radar apparatus includes: an oscillating unit configured to
generate carrier waves; a first transmission unit configured to
spread the carrier waves generated by the oscillating unit, using a
first pseudo-random code; a second transmission unit configured to
spread the carrier waves generated by the oscillating unit, using a
second pseudo-random code different from the first pseudo-random
code; a first transmission antenna that transmits first carrier
waves that are the carrier waves spread by the first transmission
unit; a second transmission antenna that transmits second carrier
waves that are the carrier waves spread by the second transmission
unit, the second carrier waves having a directional characteristic
being different from a directional characteristic of the first
carrier waves transmitted by the first transmission antenna; a
reception antenna that receives reflected waves that are the first
carrier waves and the second carrier waves that have been
transmitted respectively by the first transmission antenna and the
second transmission antenna and have been reflected from the
object; and a reception unit configured to despread the reflected
waves received by the reception antenna, using the first
pseudo-random code and to despread the reflected waves received by
the reception antenna, using the second pseudo-random code, the
first transmission antenna transmits the first carrier waves spread
by the first transmission unit, forward of the vehicle, and the
second transmission antenna transmits the second carrier waves
spread by the second transmission unit, at least forward or
diagonally forward of the vehicle.
[0040] With this configuration, the vehicle apparatus according to
the present invention transmits carrier waves that have different
directional characteristics and that have been spread using
different pseudo-random codes. Furthermore, the vehicle according
to the present invention despreads the carrier waves reflected from
an object, using 2 pseudo-random codes, respectively. Thereby, the
carrier wave having different directional characteristics can be
extracted separately and equivalently. Thus, the vehicle according
to the present invention can switch between two different detection
distances and directions of a vehicle without interposing a
switching device in a transmission path of carrier wave of several
tens of GHz. Furthermore, the vehicle according to the present
invention can detect an object by switching between a detection
range of a longer distance and a narrower angle with respect to a
front direction of the vehicle and a detection range of a shorter
distance and a wider angle with respect to an oblique forward
direction of the vehicle.
[0041] A method for controlling a radar apparatus according to the
present invention is a method for controlling a radar apparatus
that detects an object, and includes: generating carrier waves;
spreading the carrier waves using a first pseudo-random code, and
spreading the carrier waves using a second pseudo-random code
different from the first pseudo-random code; transmitting first
carrier waves and second carrier waves, the first carrier waves
being the carrier waves spread using the first pseudo-random code,
and the second carrier waves being the carrier waves spread using
the second pseudo-random code and having a directional
characteristic different from a directional characteristic of the
first carrier waves; receiving reflected waves that are the first
carrier waves and the second carrier waves and that have been
transmitted and have been reflected from the object; and
despreading the reflected waves using the first pseudo-random code,
and the reflected waves using the second pseudo-random code.
[0042] With the controlling method, carrier waves that have
different directional characteristics and that have been spread
using different pseudo-random codes are transmitted. Furthermore,
with the controlling method, the first and second carrier waves
reflected from an object are despread, using 2 pseudo-random codes,
respectively. Thereby, the first and second carrier waves having
different directional characteristics can be extracted separately
and equivalently. Thus, the controlling method according to the
present invention can switch between detection distances and
directions of a vehicle without interposing a switching device in a
transmission path of carrier wave of several tens of GHz.
[0043] As described above, the present invention can provide a
radar apparatus capable of changing detection ranges and detection
directions, a method for controlling the same, and a vehicle
including the same, without providing a switching device in a
transmission path of carrier waves.
FURTHER INFORMATION ABOUT TECHNICAL BACKGROUND TO THIS
APPLICATION
[0044] The disclosure of Japanese Patent Application No.
2007-238358 filed on Sep. 13, 2007 including specification,
drawings and claims is incorporated herein by reference in its
entirety.
BRIEF DESCRIPTION OF THE DRAWINGS
[0045] These and other objects, advantages and features of the
invention will become apparent from the following description
thereof taken in conjunction with the accompanying drawings that
illustrate a specific embodiment of the invention. In the
Drawings:
[0046] FIG. 1 illustrates a block diagram of a conventional radar
apparatus;
[0047] FIG. 2 schematically illustrates an external view of a
vehicle equipped with the radar apparatus according to the first
embodiment;
[0048] FIG. 3 illustrates a block diagram of a configuration of the
radar apparatus according to the first embodiment;
[0049] FIG. 4 illustrates a block diagram of a configuration of a
reception circuit according to the first embodiment;
[0050] FIG. 5A illustrates an example of a pseudo-random code and
spread waves in the radar apparatus according to the first
embodiment;
[0051] FIG. 5B illustrates an example of a pseudo-random code and
reflected waves in the radar apparatus according to the first
embodiment;
[0052] FIG. 5C illustrates an example of a pseudo-random code and
despread waves in the radar apparatus according to the first
embodiment;
[0053] FIG. 5D illustrates an example of a baseband radar signal in
the radar apparatus according to the first embodiment;
[0054] FIG. 6 schematically illustrates disposition of transmission
antennas and emission patterns of beams according to the first
embodiment;
[0055] FIG. 7 illustrates a block diagram of a configuration of a
variation of a reception circuit according to the first
embodiment;
[0056] FIG. 8 illustrates a block diagram of a configuration of a
variation of a reception circuit according to the first
embodiment;
[0057] FIG. 9 illustrates a block diagram of a configuration of a
radar apparatus according to the second embodiment;
[0058] FIG. 10 illustrates a block diagram of a configuration of a
reception circuit according to the second embodiment;
[0059] FIG. 11 schematically illustrates disposition of
transmission antennas and emission patterns of beams according to
the second embodiment;
[0060] FIG. 12 illustrates a configuration of transmission antennas
according to the second embodiment; and
[0061] FIG. 13 illustrates a block diagram of a configuration of a
variation of a reception circuit according to the second
embodiment.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0062] The following describes a radar apparatus according to
embodiments of the present invention with reference to
drawings.
First Embodiment
[0063] The radar apparatus according to a first embodiment of the
present invention spreads carrier waves to be transmitted so as to
cover different ranges using different pseudo-random codes.
Furthermore, the radar apparatus despreads carrier waves to be
reflected from an object using different pseudo-random codes.
Thereby, the radar apparatus can extract the multiplexed carrier
waves individually, thus enabling switching between detection
ranges without providing any switching device in a transmission
path of the carrier waves.
[0064] First, a configuration of the radar apparatus according to
the first embodiment is described.
[0065] FIG. 2 schematically illustrates an external view of a
vehicle equipped with the radar apparatus according to the first
embodiment. A vehicle 150 in FIG. 2 includes a radar apparatus 200
that is mounted in a front side of the vehicle 150. The radar
apparatus 200 is a radar apparatus that detects objects in 2
detection ranges. The radar apparatus 200 emits a beam 151 forward
of the vehicle 150, and emits a beam 152 forward and diagonally
forward of the vehicle 150. The beam 151 is emitted to a longer
distance and at a narrower angle than the beam 152.
[0066] Furthermore, the radar apparatus 200 detects an obstacle
forward of the vehicle 150 by reflection or scattering from objects
by the beams 151 and 152.
[0067] FIG. 3 illustrates a block diagram of the configuration of
the radar apparatus 200.
[0068] The radar apparatus 200 includes an oscillator 201, a
splitter 202, code generators 203A and 203B, transmission circuits
204A and 204B, transmission antennas 205A, 205B, 205C, 205D, 206B,
and 206C, gain adjustment circuits 207A, 207B, 207C, 207D, 208B,
and 208C, a reception antenna 209, a reception circuit 210, and a
signal processing circuit 211. When the antennas do not have to be
distinguished individually: the transmission antennas 205A, 205B,
205C, and 205D are collectively referred to as a transmission
antenna 205; the transmission antennas 206B and 206C are
collectively referred to as a transmission antenna 206; the gain
adjustment circuits 207A, 207B, 207C, and 207D are collectively
referred to as a gain adjustment circuit 207; and the gain
adjustment circuits 208B and 208C are collectively referred to as a
gain adjustment circuit 208.
[0069] The oscillator 201 generates carrier waves 221 at quasi
millimeter wave frequencies ranging from 20 to 30 GHz (for example,
26 GHz band) or carrier waves 221 at millimeter wave frequencies
ranging from 30 to 100 GHz (for example, 60 or 76 GHz band).
[0070] The oscillator 201 may directly generate the carrier waves
having the above-mentioned frequencies, or oscillate in a frequency
lower than the frequencies and then generate the carrier waves
having the above-mentioned frequencies using a multiplier. When the
frequency of the carrier waves 221 is 26.4 GHz, an oscillation
frequency of the oscillator 201 may be set to 26.4 GHz.
Alternatively, the oscillator 201 may generate carrier waves having
the frequency of 26.4 GHz by setting oscillation frequency of the
oscillator 201 to 8.8 GHz and by tripling frequency of a signal
oscillated by the oscillator 201 through a multiplier. Here, the
oscillator 201 includes the multiplier. Furthermore, both of the
two cases for generating carrier waves indicate that the oscillator
201 outputs carrier waves having the frequency of 26.4 GHz.
[0071] The splitter 202 generates the same carrier waves 222A and
222B by splitting the carrier waves 221.
[0072] The code generator 203A generates a pseudo-random code M1
(hereinafter referred to as a "code M1"). The code generator 203B
generates a pseudo-random code M2 (hereinafter referred to as a
"code M2"). The codes M1 and M2 are different pseudo-random codes.
In the first embodiment, the codes M1 and M2 are PN codes each
having a different pattern, and more specifically, are M-sequence
codes. Furthermore, the codes M1 and M2 are preferably M-sequence
codes having a low correlation therebetween. Here, the code
generators 203A and 203B may be integrated into a code generator,
and the resulting code generator may simultaneously generate
different codes, and output the codes.
[0073] The transmission circuit 204A spreads the carrier waves 222A
using the code M1, and generates spread waves 224A. The
transmission circuit 204B spreads the carrier waves 222B using the
code M2, and generates spread waves 224B.
[0074] The gain adjustment circuit 207 amplifies the spread waves
224A. The gain adjustment circuit 208 attenuates the spread waves
224B. More specifically, the gain adjustment circuits 207 and 208
set electric field intensity of the spread waves 224A to be
transmitted from the transmission antennas 205 to be approximately
10 times higher than that of the spread waves 224B to be
transmitted from the transmission antenna 206.
[0075] The transmission antenna 205 transmits the beam 151 by
transmitting the spread waves 224A amplified by the gain adjustment
circuit 207. The transmission antenna 206 transmits the beam 152 by
transmitting the spread waves 224B attenuated by the gain
adjustment circuit 208. Furthermore, the beam 151 emitted through
the transmission antenna 205 and the beam 152 emitted through the
transmission antenna 206 are emitted as beams having different
directional characteristics, respectively. More specifically, the
beam 151 emitted through the transmission antenna 205 covers a
range of a longer distance and a narrower angle than that of the
beam 152 emitted through the transmission antenna 206.
[0076] The reception antenna 209 receives reflected waves 229
obtained by reflection from objects with the beams 151 and 152 that
have been respectively emitted by the transmission antennas 205 and
206.
[0077] The reception circuit 210 despreads the reflected waves 229
using the code M1, and performs quadrature detection (demodulation)
on a signal corresponding to the despread reflected waves 229 to
generate a baseband radar signal 230. In other words, the reception
circuit 210 extracts reflected waves obtained by reflection from
objects with the beam 151, and generates the baseband radar signal
230 corresponding to the reflected waves. Here, a baseband radar
signal corresponds to reflected waves downconverted to a low
frequency band. The signal components are included in a reception
signal according to variations of intensity of electric waves
emitted from a radar apparatus and reflected from an object.
Furthermore, the reception circuit 210 despreads the reflected
waves 229 using the code M2, and performs quadrature detection
(demodulation) on a signal corresponding to the despread reflected
waves 229 to generate the baseband radar signal 230. In other
words, the reception circuit 210 extracts reflected waves obtained
by reflection from objects with the beam 152, and generates the
baseband radar signal 230 corresponding to the reflected waves.
[0078] The signal processing circuit 211 decides, for example, a
distance from the vehicle 150 to an object, and a relative speed
with respect to the object by performing signal processing on the
baseband radar signal 230. Here, the signal processing circuit 211
may perform the signal processing using a general radio device, and
thus the detailed description is omitted.
[0079] Next, a detailed configuration of the reception circuit 210
is described.
[0080] FIG. 4 illustrates a block diagram of the configuration of
the reception circuit 210. The reception circuit 210 includes delay
circuits 240A and 240B, a selecting circuit 241, a despreader 242,
and a quadrature detector (demodulator) 243.
[0081] The delay circuit 240A delays the code M1, and outputs the
delayed code M1. The delay circuit 240B delays the code M2, and
outputs the delayed code M2. Since delayed amounts of the codes M1
and M2 in the respective delay circuits 240A and 240B vary, the
delay circuits 240A and 240B sequentially output the delayed codes
M1 and M2 obtained by increasing or decreasing the amounts. Here,
the delayed amounts of the codes M1 and M2 in the delay circuits
240A and 240B correspond to respective distances to an object.
[0082] The selecting circuit 241 selects one of the codes M1 and M2
that are delayed by the delay circuits 240A and 240B,
respectively.
[0083] The received reflected waves 229 are amplified by a low
noise amplifier (not illustrated).
[0084] After the reception antenna 209 receives the reflected waves
229 using the code M1 or M2 selected by the selecting circuit 241,
the despreader 242 despreads the reflected waves 229 amplified by
the low noise amplifier, and outputs despread waves 252.
[0085] The quadrature detector 243 performs quadrature detection on
the despread waves 252 using the carrier waves 221 generated by the
oscillator 201, and generates the baseband radar signal 230. Here,
quadrature detection is generally performed by vectoring waves
using carrier waves having a different phase by 90 degrees, as an
in-phase component and a quadrature component.
[0086] Next, specific examples of processing in the transmission
circuits 204A and 204B, and the reception circuit 210 are
described.
[0087] The transmission circuits 204A and 204B spread a spectrum of
carrier waves by performing Binary Phase Shift Keying (BPSK)
modulation on a pseudo-random code using the carrier waves. FIG. 5A
illustrates a relationship between the code M1 and the spread waves
224A. As illustrated in FIG. 5A, the transmission circuit 204A
maintains a phase of the carrier waves 222A in a chip corresponding
to a logical value "0" of the code M1, and generates the spread
waves 224A obtained by inverting the phase of the carrier waves
222A in a chip corresponding to a logical value "1" of the code M1.
Here, the chips indicate respective periods of time corresponding
to a bit of a pseudo-random code. For example, a 2.5 Gcps code may
be used as a chip rate.
[0088] Here, the transmission circuit 204B (also) maintains a phase
of the carrier waves 222B in a chip corresponding to a logical
value "0" of the code M2, and generates the spread waves 224B
obtained by inverting the phase of the carrier waves 222B in a chip
corresponding to a logical value "1" of the code M2.
[0089] Hereinafter, a case where the reception circuit 210 performs
despreading and quadrature detection using the code M1 is
described.
[0090] FIG. 5B illustrates a relationship between the code M1
delayed by the delay circuit 240A and the reflected waves 229. FIG.
5C illustrates a relationship between the code M1 delayed by the
delay circuit 240A and the despread waves 252. Here, FIGS. 5B and
5C illustrate examples when an object is present at a distance
corresponding to a delayed amount in the delay circuit 240A. FIG.
5D illustrates an example of the baseband radar signal 230.
[0091] As illustrated in FIG. 5B, when an object is present within
an incident range of the beam 151, the reception antenna 209
receives the reflected waves 229 having the same waveform pattern
as that of the spread waves 224A. Furthermore, when an object is
present within an incident range of the beam 152, the reception
antenna 209 receives the reflected waves 229 having the same
waveform pattern as that of the spread waves 224B. Furthermore,
when no object is present within the incident ranges of the beams
151 and 152, the reception antenna 209 does not receive the
reflected waves 229.
[0092] The delay circuit 240A delays the code M1 by changing the
delayed amount sequentially. The despreader 242 despreads the
reflected waves 229 using the code M1 delayed by the delay circuit
240A.
[0093] When an object is present within an incident range of the
beam 151, and an amount delayed by the delay circuit 240A
corresponds to a distance to the object, as illustrated in FIG. 5C,
the despreader 242 generates the despread waves 252 having the same
waveform pattern as that of the carrier waves 221. Otherwise,
except for the aforementioned cases, the despreader 242 generates
the despread waves 252 having a different waveform pattern as that
of the carrier waves 221. In other words, the despreader 242
generates the despread waves 252 having a different waveform
pattern as that of the carrier waves 221, in the case where: an
object is present within the incident range of the beam 152; no
object is present within the incident ranges of the beams 151 and
152; or an object is present within the incident range of the beam
151 but an amount delayed by the delay circuit 240A does not
correspond to a distance to the object.
[0094] Here, the case where a delayed amount corresponds to a
distance to an object indicates that the delayed amount in the
delay circuit 240A matches a period of time during which the
emitted beam 151 is transmitted, reflected from an object, and is
received by the reception antenna 209.
[0095] Next, the quadrature detector 243 performs quadrature
detection on the despread waves 252 using the carrier waves
221.
[0096] As illustrated in FIG. 5D, when an object is present within
an incident range of the beam 151, and an amount delayed by the
delay circuit 240A corresponds to a distance to the object, the
quadrature detector 243 outputs a first value indicating that the
object is present, as the baseband radar signal 230. This is
because the waveform pattern of the despread waves 252 matches that
of the carrier waves 221. Otherwise in other cases, since the
waveform pattern of the despread waves 252 does not match that of
the carrier waves 221, the quadrature detector 243 outputs a second
value indicating that no object is present, as the baseband radar
signal 230.
[0097] More specifically, a maximal value corresponding to an
amount delayed by the delay circuit 240A is determined. When the
delayed amount reaches the maximal value, the delay circuit 240A
initializes the amount to an initial value (for example, 0).
Thereby, the reception circuit 210 can repeatedly scan codes within
a range from a delayed amount 0 to the maximal delayed amount. The
scan repetition time (scan frequency) determines distinctive
features of the radar apparatus 200, such as a time resolution
(corresponding to a repetition time), a distance resolution (a
distance corresponding to a time period corresponding to one
delayed amount), and a detectable distance (a maximum detection
range).
[0098] Furthermore, in the case where an object is present within a
maximal detection distance, a value of the baseband radar signal
230 varies according to the presence or absence of the object and a
position of the object. In other words, the baseband radar signal
230 is a signal having a bandwidth corresponding to a time period
of a distance resolution.
[0099] The beam 151 is exemplified in FIGS. 5A to 5D. Since a case
using the beam 152 is similar to that of the beam 151 except for
the code M2 to be used for the beam 152, the description of the
beam 152 is omitted.
[0100] Accordingly, the radar apparatus 200 according to the first
embodiment of the present invention transmits the spread waves 224A
spread by the code M1, and the spread waves 224B spread by the code
M2. Furthermore, the radar apparatus 200 despreads and performs
quadrature detection on the reflected waves 229 reflected from an
object, using the codes M1 and M2, respectively.
[0101] Since the codes M1 and M2 have a low correlation, only
autocorrelation of the code M1 and the code M2 need to be
respectively considered for despreading processing. To put it
simply, assume only a case where each of the codes M1 (code in a
spread wave and delayed code from a delay circuit) and each of the
codes M2 has a uniform phase respectively (autocorrelation function
(i) between a code M1 and the delayed code M1 of a received signal
and (ii) between a code M2 and the delayed code M2 of a received
signal peaks, in other words, has a maximum value). In the case of
despreading the reflected waves 229 corresponding to the beam 151
using the code M1, the same waveform as that of the original
carrier waves 221 is reconstructed. In contrast, in the case of
despreading the reflected waves 229 corresponding to the beam 152
using the code M1, the same waveform as that of the original
carrier waves 221 is not reconstructed. Furthermore, in the case of
despreading the reflected waves 229 corresponding to the beam 152
using the code M2, the same waveform as that of the original
carrier waves 221 is reconstructed. In contrast, in the case of
despreading the reflected waves 229 corresponding to the beam 151
using the code M2, the same waveform as that of the original
carrier waves 221 is not reconstructed.
[0102] In reality, since the waveform of the reflected waves 229 is
attenuated or distorted by free space propagation, the waveform
obtained by despreading the reflected waves 229 is not exactly the
same as that of the original carrier waves 221. Here, a state where
a phase is smoothly continuous is referred to as "same as that of
the carrier waves 221".
[0103] Thereby, the reception circuit 210 can extract the beams 151
and 152 each having a different directional characteristic. In
other words, such extraction is equivalent to selection of only an
emission pattern from the transmission antenna 205 from among
emission patterns emitted from the transmission antennas 205 and
206. Thus, the radar apparatus 200 can switch between detection
distances and directions without having a switching device in a
transmission path of several tens of GHz.
[0104] Here, the radar apparatus 200 includes the selecting circuit
241 that only functions as a circuit that switches between the
codes M1 and M2 that are logical values. The selecting circuit 241
may be composed of a simple logical circuit (for example, a 2-input
multiplexer or a selector). In other words, the selecting circuit
241 does not affect any carrier waves of several tens of GHz,
unlike a switching device for use in a conventional radar
apparatus.
[0105] Next, disposition of the transmission antennas 205 and 206
and characteristics of the beams 151 and 152 are described.
[0106] FIG. 6 schematically illustrates the disposition of the
transmission antennas 205 and 206 and emission patterns of the
beams 151 and 152.
[0107] As illustrated in FIG. 6, the transmission antennas 205 are
disposed linearly in a longitudinal direction of FIG. 6.
Furthermore, the transmission antennas 205 are disposed at equal
intervals illustrated as intervals "d" in FIG. 6. In other words,
the transmission antennas 205 are disposed symmetric with respect
to a horizontal direction of FIG. 6. Thereby, a symmetric detection
range with respect to right and left directions of the vehicle 150
can be achieved.
[0108] The transmission antennas 206 are disposed linearly in the
longitudinal direction of FIG. 6. Furthermore, the transmission
antennas 206 are disposed at equal intervals illustrated as
intervals "d" in FIG. 6. In other words, the transmission antennas
206 are disposed symmetric with respect to the horizontal direction
of FIG. 6. Thereby, a symmetric detection range with respect to
right and left directions of the vehicle 150 can be achieved.
[0109] Furthermore, each of the transmission antennas 205 and 206
is an antenna having an identical shape. Furthermore, the
transmission antenna 206B is paired with the transmission antenna
205B, and they are disposed closer each other. Furthermore, the
transmission antenna 206C is paired with the transmission antenna
205C, and they are disposed closer each other. Furthermore, in the
longitudinal direction of FIG. 6, the transmission antennas 205B
and 205C respectively paired with the transmission antennas 206B
and 206C are sandwiched between the transmission antennas 205A and
205D that are not paired with any of the transmission antennas 206.
In other words, the transmission antennas 205B and 205C
respectively paired with the transmission antennas 206B and 206C
are disposed linearly inward of the transmission antennas 206A and
206D with respect to the longitudinal direction of FIG. 6.
[0110] Furthermore, the gain adjustment circuits 207 and 208 set
electric field intensity of the beam 152 to be approximately 10
times lower than that of electric field intensity of the beam
151.
[0111] In general, as a linear array antenna including the N number
of antenna elements disposed at equal intervals "d", where N is an
integer of one or more, has larger number of N, a main lobe gets
sharper directivity. In contrast, as the linear array antenna has
smaller number of N, the main lobe gets broader directivity.
Furthermore, as electric field intensity of a beam is higher, the
beam is emitted at a longer distance.
[0112] The directivity E (.theta.) of the electric field intensity
of the linear array antenna including the N number of antenna
elements is expressed by Equation 1 below, where directivity of
each of the antenna elements is e (.theta.), a magnitude of a
current to be supplied to each of the antenna elements (element
current) is In, and a wave number is kd. For simplification of the
equation, a phase of the element current is defined to be 0.
E ( .theta. ) = e ( .theta. ) n = 0 N - 1 I n exp ( j nkd sin
.theta. ) = e ( .theta. ) I sin ( Nkd sin .theta. / 2 ) sin ( kd
sin .theta. / 2 ) [ Equation 1 ] ##EQU00001##
[0113] Thus, when the electric field intensity of the beam 152 is
small enough, the electric field intensity of the beam 151 emitted
from the transmission antennas 205 as a linear array antenna
including 4 antenna elements is expressed by the directivity E1
(.theta.) calculated from Equation 2. Here, the element current of
each of the transmission antennas 205 is collectively expressed by
I1, and the directivity of each of the transmission antennas 205 is
collectively expressed by e (.theta.).
E1(.theta.)=e(.theta.).times.I1.times.[exp(j0 kd sin
.theta.)+exp(j1 kd sin .theta.)+exp(j2 kd sin .theta.)+exp(j3 kd
sin .theta.)] [Equation 2]
[0114] In contrast, the electric field intensity of the beam 152
emitted from the transmission antennas 206 as an array antenna
including 2 antenna elements is expressed by the directivity E2
(.theta.) calculated from Equation 3. Here, the element current of
each of the transmission antennas 206 is collectively expressed by
I2, and the directivity of each of the transmission antennas 206 is
collectively expressed by e (.theta.), where I2<I1.
E2(.theta.)=e(.theta.).times.I2.times.[exp(j1 kd sin
.theta.)+exp(j2 kd sin .theta.)] [Equation 3]
[0115] An emission pattern obtained by combining the beams 151 and
152 respectively emitted from the transmission antennas 205 and 206
may be calculated using both Equations 2 and 3. Thus, the emission
pattern may be expressed by Equation 4 below.
E1(.theta.)+E2(.theta.)=e(.theta.).times.[I1.times.exp(j0 kd sin
.theta.)+(I1+I2)*exp(j1 kd sin .theta.)+(I1+I2).times.exp(j2 kd sin
.theta.)+I1.times.exp(j3 kd sin .theta.)] [Equation 4]
[0116] As described above, compared to an electric field pattern
and electric field intensity of the beam 151 emitted from the
transmission antenna 205 and those of the beam 152 emitted from the
transmission antenna 206, a main lobe of the beam 151 has sharper
directivity and is emitted at a longer distance. In contrast, a
main lobe of the beam 152 has broader directivity, and the electric
field intensity is smaller. Thus, the beam 152 is emitted at a
shorter distance and a broader angle.
[0117] As described above, directivities (detection ranges) of the
beams 151 and 152 may be optionally designed using above Equations
1 to 4.
[0118] Consequently, the radar apparatus 200 according to the first
embodiment can emit, forward of the vehicle 150, the beam 151
having a pattern of a longer distance and a narrower angle, and
emit, forward and obliquely forward of the vehicle 150, the beam
152 having a pattern of a shorter distance and a broader angle.
[0119] Furthermore, the transmission antenna 206B is paired with
the transmission antenna 205B, and the transmission antenna 206C is
paired with the transmission antenna 205C. The paired transmission
antennas are respectively disposed closer each other. Furthermore,
the pair of transmission antennas 205B and 206B and the pair of
transmission antennas 205C and 206C are sandwiched between the
transmission antennas 205A and 205D that are not paired with any of
the transmission antennas. Thereby, the transmission antennas 205
and the transmission antennas 206 may be respectively designed as
linear array antennas while incident ranges of the beams 151 and
152 are kept symmetric with respect to the right and left
directions of the vehicle 150.
[0120] The description of the radar apparatus 200 according to the
first embodiment above will not limit the scope of the present
invention.
[0121] For example, although the reception circuit 210 has the
configuration illustrated in FIG. 4 in the aforementioned
description, the configuration may be one of two configurations
described in the following paragraphs.
[0122] FIG. 7 illustrates a block diagram of the configuration of a
reception circuit 210A of the first variation of the reception
circuit 210. The constituent elements in FIG. 7 identical to those
of FIG. 4 are numbered in the same manner as in FIG. 4, and thus
the description is omitted.
[0123] The reception circuit 210A in FIG. 7 includes delay circuits
240A and 240B, despreaders 242A and 242B, quadrature detectors 243A
and 243B, and a splitter 261.
[0124] The splitter 261 splits the reflected waves 229 received by
the reception antenna 209 into the same reflected waves 271A and
271B.
[0125] The despreader 242A despreads the reflected waves 271A using
the code M1 delayed by the delay circuit 240A, and outputs despread
waves 252A. The despreader 242B despreads the reflected waves 271B
using the code M2 delayed by the delay circuit 240B, and outputs
despread waves 252B.
[0126] The quadrature detector 243A performs quadrature detection
on the despread waves 252A using the carrier waves 221 generated by
the oscillator 201, and generates a baseband radar signal 230A. The
quadrature detector 243B performs quadrature detection on the
despread waves 252B using the carrier waves 221 generated by the
oscillator 201, and generates a baseband radar signal 230B. The
signal processing circuit 211 decides a distance from the vehicle
150 to an object, and a relative speed with respect to the object
by performing signal processing on the baseband radar signals 230A
and 230B.
[0127] As such, the reception circuit 210A can perform both
despreading and quadrature detection on reflected waves in parallel
using the codes M1 and M2. Thus, the processing speed of the
reception circuit 210A can be improved. Furthermore, the signal
processing circuit 211 can perform signal processing on the
baseband radar signals 230A and 230B in parallel. Thus, the
processing speed of the radar apparatus 200 can be improved.
[0128] FIG. 8 illustrates a block diagram of the configuration of a
reception circuit 210B of the second variation of the reception
circuit 210. The constituent elements in FIG. 8 identical to those
of FIG. 7 are numbered in the same manner as in FIG. 7, and thus
the description is omitted.
[0129] The reception circuit 210B in FIG. 8 is different from the
reception circuit 210A in excluding the splitter 261. Furthermore,
as illustrated in FIG. 8, the radar apparatus 200 includes two
reception antennas 209A and 209B.
[0130] The reception antenna 209A receives reflected waves 229A
obtained by reflection from objects with the beams 151 and 152 that
have been respectively transmitted by the transmission antennas 205
and 206. The reception antenna 209B receives reflected waves 229B
obtained by reflection from objects with the beams 151 and 152 that
have been respectively transmitted by the transmission antennas 205
and 206. In other words, the reflected waves 229A and 229B are
reflected waves of the same waveform pattern.
[0131] The despreader 242A despreads the reflected waves 229A using
the code M1 delayed by the delay circuit 240A, and outputs the
despread waves 252A. The despreader 242B despreads the reflected
waves 229B using the code M2 delayed by the delay circuit 240B, and
outputs the despread waves 252B.
[0132] As such, the reception circuit 210B can perform both
despreading and quadrature detection on waves in parallel using the
codes M1 and M2. Thus, the processing speed of the reception
circuit 210B can be improved. Furthermore, the signal processing
circuit 211 can perform signal processing on the baseband radar
signals 230A and 230B in parallel. Thus, the processing speed of
the radar apparatus 200 can be improved.
[0133] Although the radar apparatus 200 is installed in a front
side of the vehicle 150 in the aforementioned description, the
radar apparatus 200 may be installed in a rear side or a lateral
side of the vehicle 150. Furthermore, the radar apparatus 200 may
be installed in 2 or more portions from among the front side, rear
side, and lateral side of the vehicle 150.
[0134] Furthermore, although the radar apparatus 200 switches
between 2 patterns of detection ranges in the aforementioned
description, the radar apparatus 200 may switch between 3 or more
patterns of detection ranges.
[0135] Furthermore, although the transmission antennas 205 and 206
have the identical shape in the aforementioned description, they
may have different shapes.
[0136] Furthermore, although the gain adjustment circuit 207
amplifies the spread waves 224A and the gain adjustment circuit 208
attenuates the spread waves 224B in the aforementioned description,
the gain adjustment circuits 207 and 208 may amplify the spread
waves 224A or attenuate the spread waves 224B. In this case, the
radar apparatus 200 may exclude the gain adjustment circuit 207 or
208 that does not adjust a gain.
Second Embodiment
[0137] The first embodiment describes examples of spreading and
despreading of waves using different M-sequence codes. In contrast,
the second embodiment describes a radar apparatus that spreads and
despreads waves using different gold codes.
[0138] FIG. 9 illustrates a block diagram of a configuration of a
radar apparatus 300 according to the second embodiment. The
constituent elements in FIG. 9 identical to those of FIG. 3 are
numbered in the same manner as in FIG. 3, and thus the description
is omitted.
[0139] The radar apparatus 300 is different from the radar
apparatus 200 of the first embodiment in use of gold codes and
disposition of transmission antennas.
[0140] The radar apparatus 300 includes an oscillator 201, a
splitter 202, code generators 203A, 203B, and 203C, OR circuits
312A and 312B, transmission circuits 304A and 304B, transmission
antennas 305A, 305B, 306A, and 306B, gain adjustment circuits 307A,
307B, 308A, and 308B, a reception antenna 209, a reception circuit
310, and a signal processing circuit 211. When antennas do not have
to be distinguished from each other, the transmission antennas 305A
and 305B are collectively referred to as a transmission antenna
305. Alternatively, the transmission antennas 306A and 306B are
collectively referred to as a transmission antenna 306. When
circuits do not have to be distinguished from each other, the gain
adjustment circuits 307A and 307B are collectively referred to as a
gain adjustment circuit 307. Alternatively, the gain adjustment
circuits 308A and 308B are collectively referred to as a gain
adjustment circuit 308.
[0141] The code generator 203C generates a pseudo-random code M3
(hereinafter referred to as a "code M3"). The codes M1, M2, and M3
are different pseudo-random codes. In the second embodiment, the
codes M1, M2, and M3 are PN codes each having a different pattern,
and more specifically, are different M-sequence codes. Furthermore,
the codes M1, M2, and M3 are preferably M-sequence codes having a
low correlation therebetween.
[0142] The OR circuit 312A generates a gold code (M1+M2) obtained
through an exclusive OR of the codes M1 and M2. The OR circuit 312B
generates a gold code (M1+M3) obtained through an exclusive OR of
the codes M1 and M3.
[0143] The transmission circuit 304A spreads the carrier waves 222A
using the gold code (M1+M2), and generates spread waves 324A. The
transmission circuit 304B spreads the carrier waves 222B using the
gold code (M1+M3), and generates spread waves 324B.
[0144] The gain adjustment circuit 307 amplifies the spread waves
324A. The gain adjustment circuit 308 attenuates the spread waves
324B. More specifically, the gain adjustment circuits 307 and 308
set electric field intensity of the spread waves 324A to be
transmitted from the transmission antenna 305 to approximately 10
times higher than that of the spread waves 324B to be transmitted
from the transmission antenna 306.
[0145] The transmission antenna 305 emits a beam 153 by
transmitting the spread waves 324A amplified by the gain adjustment
circuit 307. The transmission antenna 306A emits a beam 154A by
transmitting the spread waves 324B attenuated by the gain
adjustment circuit 308. The transmission antenna 306B emits a beam
154B by transmitting the spread waves 324B attenuated by the gain
adjustment circuit 308. Furthermore, the beams 153, 154A, and 154B
to be emitted have different directional characteristics of carrier
waves. More specifically, the beam 153 is emitted at a longer
distance and at a narrower angle than those of the beams 154A and
154B.
[0146] The reception antenna 209 receives reflected waves 329
obtained by reflection from objects with the beams 153, 154A, and
154B that have been respectively transmitted by the transmission
antennas 305, 306A, and 306B.
[0147] Furthermore, the reception circuit 310 despreads the
reflected waves 329 using the code (M1+M2), and performs quadrature
detection (demodulation) on the despread signal to generate a
baseband radar signal 330. In other words, the reception circuit
310 extracts reflected waves obtained by reflection from objects
with the beam 153, and generates the baseband radar signal 330
corresponding to the reflected waves. Furthermore, the reception
circuit 310 despreads the reflected waves 329 using the code
(M1+M3), and performs quadrature detection (demodulation) on the
despread signal to generate the baseband radar signal 330. In other
words, the reception circuit 310 extracts reflected waves obtained
by reflection from objects with the beams 154A and 154B, and
generates the baseband radar signal 330 corresponding to the
reflected waves.
[0148] FIG. 10 illustrates a block diagram of a configuration of
the reception circuit 310.
[0149] The reception circuit 310 in FIG. 10 includes delay circuits
340A and 340B, despreaders 342A and 342B, quadrature detectors 343A
and 343B, and a splitter 361.
[0150] The delay circuit 340A delays the gold code (M1+M2), and
outputs the delayed code (M1+M2). The delay circuit 340B delays the
gold code (M1+M3), and outputs the delayed code (M1+M3). Since
delayed amounts of the codes in the respective delay circuits 340A
and 340B vary, the delay circuits 340A and 340B output the codes
(M1+M2) and (M1+M3) obtained by increasing or decreasing the
delayed amounts sequentially. Here, the delayed amounts of the
codes M1, M2, and M3 in the delay circuits 340A and 340B correspond
to respective distances to an object.
[0151] The splitter 361 splits the reflected waves 329 received by
the reception antenna 209 into the same reflected waves 371A and
371B.
[0152] The despreader 342A despreads the reflected waves 371A using
the code (M1+M2) delayed by the delay circuit 340A, and outputs
despread waves 352A. The despreader 342B despreads the reflected
waves 371B using the code (M1+M3) delayed by the delay circuit
340B, and outputs despread waves 352B.
[0153] The quadrature detector 343A performs quadrature detection
on the despread waves 352A using the carrier waves 221 generated by
the oscillator 201, and generates a baseband radar signal 330A. The
quadrature detector 343B performs quadrature detection on the
despread waves 352B using the carrier waves 221 generated by the
oscillator 201, and generates a baseband radar signal 330B. The
signal processing circuit 211 detects a distance from the vehicle
150 to an object, and a relative speed with respect to the object
by performing signal processing on the baseband radar signals 330A
and 330B.
[0154] With the aforementioned configuration, the radar apparatus
300 according to the second embodiment can have the same advantages
as those of the radar apparatus 200 according to the first
embodiment.
[0155] Furthermore, the radar apparatus 300 spreads and despreads
waves using gold-sequence pseudo-random codes. Thus, even when the
number of beams to be emitted increases, the radar apparatus 300
can generate various pseudo-random codes easily and use the codes
for spreading and despreading waves.
[0156] Furthermore, the reception circuit 310 can perform both
despreading and quadrature detection on waves in parallel using the
codes (M1+M2) and (M1+M3). Thus, the processing speed of the
reception circuit 310 can be improved. Furthermore, the signal
processing circuit 211 can perform signal processing on the
baseband radar signals 330A and 330B in parallel. Thus, the
processing speed of the radar apparatus 300 can be improved.
[0157] Here, the reception circuit 310 may include the selecting
circuit 241 as illustrated in FIG. 4. Furthermore, as illustrated
in FIG. 8, the radar apparatus 300 may include two reception
antennas 209A and 209B without the splitter 361.
[0158] Next, disposition of the transmission antennas 305 and 306
and characteristics of the beams 153, 154A, and 154B are
described.
[0159] FIG. 11 schematically illustrates disposition of the
transmission antennas 305 and 306 and emission patterns of the
beams 153, 154A, and 154B.
[0160] As illustrated in FIG. 11, the transmission antennas 305 and
306 are disposed linearly in a longitudinal direction. Furthermore,
the transmission antennas 305 and 306 are disposed symmetric with
respect to a lateral direction of FIG. 11.
[0161] The transmission antenna 305 functions as an array antenna
including 2 antenna elements. The transmission antennas 306A and
306B function each as an antenna including a single antenna
element.
[0162] FIG. 12 illustrates a configuration of the transmission
antennas 305 and 306. As illustrated in FIG. 12, the transmission
antennas 305A and 305B are linear array antennas including 4
antenna elements, respectively. The transmission antennas 306A and
306B are linear array antennas including 2 antenna elements,
respectively. The antenna elements included in each of the
transmission antennas 305A, 305B, 306A, and 306B are disposed
linearly.
[0163] The transmission antenna 305 emits the beam 153 having a
pattern of a longer distance and a narrower angle forward of the
vehicle 150. The transmission antenna 306A emits the beam 154A
having a pattern of a shorter distance and a broader angle
diagonally forward left of the vehicle 150. The transmission
antenna 306B emits the beam 154B having a pattern of a shorter
distance and a broader angle diagonally forward right of the
vehicle 150. The beam 155 illustrated in FIGS. 11 and 12 is a beam
obtained by combining the beams 153, 154A, and 154B.
[0164] Consequently, the radar apparatus 300 according to the
second embodiment can emit: the beam 153 having a pattern of a
longer distance and a narrower angle, forward of the vehicle 150;
the beam 154A having a pattern of a shorter distance and a broader
angle, diagonally forward left of the vehicle 150; and the beam
154B having a pattern of a shorter distance and a broader angle,
diagonally forward right of the vehicle 150.
[0165] Furthermore, a reception circuit described as following may
be used instead of the reception circuit 310.
[0166] FIG. 13 illustrates a block diagram of a configuration of a
reception circuit 310A as a variation of the reception circuit 310.
The constituent elements in FIG. 13 identical to that of FIG. 10
are numbered in the same manner as in FIG. 10, and thus the
description is omitted.
[0167] The reception circuit 310A illustrated in FIG. 13 can
extract spread waves spread by gold codes (M1+M2), (M1+M3), and
(M2+M3) in combination of any codes of M1, M2, and M3.
[0168] The reception circuit 310A includes delay circuits 380A,
380B, and 380C, a selecting circuit 341, despreaders 382A, 382B,
and 382C, and a quadrature detector 383.
[0169] The delay circuit 380A delays the code M1, and outputs the
delayed code M1. The delay circuit 380B delays the code M2, and
outputs the delayed code M2. The delay circuit 380C delays the code
M3, and outputs the delayed code M3. Since delayed amounts of the
codes M1, M2, and M3 in the respective delay circuits 380A, 380B,
and 380C vary, the delay circuits 380A, 380B, and 380C output the
codes M1, M2 and M3 obtained by increasing or decreasing the
amounts sequentially.
[0170] The selecting circuit 341 supplies the codes M1, M2, and M3
to the despreaders 382A, 382B, and 382C. In other words, the
selecting circuit 341 assigns the different codes M1, M2, and M3 to
the despreaders 382A, 382B, and 382C.
[0171] The despreader 382A despreads the reflected waves 329 using
one of the codes M1, M2, and M3 assigned by the selecting circuit
341, and outputs despread waves 392A.
[0172] The despreader 382B despreads the reflected waves 329 using
one of the codes M1, M2, and M3 assigned by the selecting circuit
341, and outputs despread waves 392B.
[0173] The despreader 382C despreads the reflected waves 329A and
392B using one of the codes M1, M2, and M3 assigned by the
selecting circuit 341.
[0174] Next, operations of the reception circuit 310A are
described. As an example, an operation of the reception circuit
310A when spread waves spread by the gold codes (M1+M2) and (M1+M3)
are extracted is described.
[0175] For example, the selecting circuit 341 supplies the code M2
to the despreader 382A, the code M3 to the despreader 382B, and the
code M1 to the despreader 382C.
[0176] The despreader 382A despreads the reflected waves 329 using
the code M2, and outputs the despread waves 392A. The despreader
382B despreads the reflected waves 329 using the code M3, and
outputs the despread waves 392B.
[0177] The despreader 382C despreads the reflected waves 329A and
392B using the code M1, and outputs despread waves 392C.
[0178] As such, the reflected waves 329 are despread by the
despreaders 382A and 382C, using the codes M1 and M2. This
operation is the same as despreading using the gold code (M1+M2).
In the same manner, the reflected waves 329 are despread by the
despreaders 382B and 382C, using the codes M1 and M3. This
operation is the same as despreading using the gold code (M1+M3).
Thus, when an object is present within detection ranges of the
beams 153, 154A, and 154B, the despread waves 392C corresponds to a
pattern of the carrier waves 221. In other words, the reception
circuit 310A can extract spread waves spread by the gold codes
(M1+M2) and (M1+M3).
[0179] Here, the despreaders 382A and 382C, and the despreaders
382B and 382C despread reflected waves for a sufficiently short
period of time with respect to one chip period (inverse of chip
rate). Here, one chip period is a period corresponding to one bit
of a pseudo-random code. For example, one chip period is
approximately 1/10 of a cycle of carrier waves.
[0180] Furthermore, when the selecting circuit 341 changes codes
assigned to the despreaders 382A, 382B, and 382C, the reception
circuit 310A can extract the reflected waves 329 spread by gold
codes determined in combination of any two codes. Thus, the
reception circuit 310A can extract only reflected waves 329 spread
by such gold codes selected from among different gold codes used
for spreading reflected waves 329. For example, codes assigned to
the despreaders 382A, 382B, and 382C are defined to be M2, M3, and
M1, respectively, and thus the reception circuit 310A can extract
other than the reflected waves spread by the gold code (M2+M3) when
beams spread by the codes (M1+M2), (M1+M3), and (M2+M3) are
simultaneously emitted and the reception antenna 209 receives the
reflected waves.
[0181] Furthermore, although the radar apparatus 300 switches
between 2 patterns of detection ranges in the aforementioned
description, the radar apparatus 300 may switch between 3 or more
patterns of detection ranges. When switching between 3 or more
patterns of detection ranges, the radar apparatus 300 may include
an OR circuit and use a gold code (M2+M3).
[0182] Furthermore, although the transmission antenna 305 is an
linear array antenna including 4 antenna elements and the
transmission antenna 306 is an linear array antenna including 2
antenna elements in the aforementioned description, the
transmission antennas 305 and 306 have only to include at least one
antenna element. For example, the transmission antennas 305 and 306
may be linear array antennas including the same number of antenna
elements.
[0183] Furthermore, although the gain adjustment circuit 307
amplifies the spread waves 324A and the gain adjustment circuit 308
attenuates the spread waves 324B in the aforementioned description,
the gain adjustment circuits 307 and 308 may amplify the spread
waves 324A or attenuate the spread waves 324B. In this case, the
radar apparatus 300 may exclude the gain adjustment circuit 307 or
308 that does not adjust a gain.
[0184] Furthermore, although the radar apparatus 300 includes the
transmission antennas 305 and 306 disposed as illustrated in FIG.
11, it may include the transmission antennas disposed as
illustrated in FIG. 6. Furthermore, the radar apparatus 200
according to the first embodiment may include the transmission
antenna disposed as illustrated in FIG. 11.
[0185] Furthermore, as illustrated in FIG. 6, the radar apparatus
300 may include the transmission antennas 305 that are larger than
the transmission antennas 306 in number, and the transmission
antennas 306 may be paired with some of the transmission antennas
305 and be closely disposed each other. More specifically, the
other transmission antennas 305 that are not paired with the
transmission antennas 306 may be sandwiched between the pairs of
transmission antennas 305 and 306 in a longitudinal direction.
[0186] Furthermore, the transmission antennas 205, 206, 305, and
306 may be designed and have the configuration including the number
of the antennas and the disposition so as to have necessary
emission patterns of beams, regardless of configurations of the
linear array antennas described in the first and second
embodiments. For example, the transmission antennas 205, 206, 305,
and 306 are not limited to array antennas but may be antennas each
including a single antenna element. Furthermore, the number of the
transmission antennas 205, 206, 305, and 306 may be increased.
[0187] Furthermore, although in the aforementioned description, the
gain adjustment circuits 207 and 307 amplify the spread waves 224A
and 324A, respectively, and the gain adjustment circuits 208 and
308 attenuate the spread waves 224B and 324B, respectively, the
gain adjustment circuits 207, 208, 307, and 308 may be anything as
long as they adjust a gain of a beam emitted from the transmission
antennas 205 and 305 to be larger than a gain of the beam emitted
from the transmission antennas 206 and 306. For example, the
carrier waves 222A and 222B may be amplified or attenuated by
providing the gain adjustment circuits 207, 208, 307, and 308 in a
front stage of the transmission circuits 204A, 204B, 304A, and
304B.
[0188] Furthermore, the radar apparatuses 200 and 300 may adjust a
gain of a beam emitted from the transmission antennas 205 and 305
to be larger than a gain of a beam emitted from the transmission
antennas 206 and 306 by excluding the gain adjustment circuits 207,
208, 307, and 308, and changing the configurations of the
transmission antennas 205, 206, 305, and 306.
[0189] Furthermore, although the reception circuits 210, 210A,
210B, 310, and 310A include the quadrature detectors 243, 243A,
243B, 343A, 343B, and 383 that perform detection using a quadrature
component, the reception circuits 210, 210A, 210B, 310, and 310A
may include a synchronous detector that performs detection using an
in-phase component instead of the quadrature detectors 243, 243A,
243B, 343A, 343B, and 383.
[0190] Furthermore, although the radar apparatuses 200 and 300
perform homodyne detection (direct conversion) using the carrier
waves 221 generated by the oscillator 201 in the aforementioned
description, the present invention may be applicable to a radar
apparatus that performs heterodyne detection using other
frequencies at a reception side.
[0191] Although only some exemplary embodiments of this invention
have been described in detail above, those skilled in the art will
readily appreciate that many modifications are possible in the
exemplary embodiments without materially departing from the novel
teachings and advantages of this invention. Accordingly, all such
modifications are intended to be included within the scope of this
invention.
INDUSTRIAL APPLICABILITY
[0192] The present invention may be applicable to a radar
apparatus, in particular to an on-vehicle radar apparatus that
detects an obstacle and other objects.
* * * * *